CN106129217A - There is high brightness AlGaInP light emitting diode and the manufacture method thereof of AZO roughened layer - Google Patents

Abstract

A high-brightness AlGaInP light-emitting diode with an AZO roughened layer and a manufacturing method thereof belong to the technical field of LED production and application. The N electrode is arranged on the back of the substrate, and the N-GaAs buffer layer, AlAs/AlGaAs reflective layer, N ‑AlGaInP lower confinement layer, MQW multi-quantum well active layer, P‑AlGaInP upper confinement layer, P‑GaInP buffer layer and P‑GaP current spreading layer, AZO transparent conductive layer is set on the surface of P‑GaP current spreading layer, in part The P electrode is arranged on the surface of the AZO transparent conductive layer, and an AZO roughened layer is arranged on the surface of another part of the AZO transparent conductive layer. The AZO transparent conductive layer has good current spreading ability, which reduces the accumulation of current in a local area and improves the luminous efficiency.

Description

High-brightness AlGaInP light-emitting diode with AZO roughened layer and its manufacturing method

technical field

The invention belongs to the technical field of LED production and application, and in particular relates to a production process of an AlGaInP light-emitting diode, especially a chip thereof.

Background technique

Quaternary AlGaInP light-emitting diodes are widely used in various devices for indication and display due to their high luminous efficiency, wide color range, low power consumption, long life, monochromatic light emission, fast response, impact resistance, and small size. In terms of automotive interior indicator lights, home appliance indicator lights, traffic stop lights, and household lighting, how to meet the market's large demand for high-brightness chips and improve the brightness of LED chips has become the research focus of LED companies. Conventional vertical structure AlGaInP light-emitting diodes are based on the P-GaP current spreading layer for lateral expansion, injecting current into the light-emitting area, but due to the limited current spreading ability of P-GaP, the current density in the area near the bottom of the electrode is higher, and the current in the area farther away from the electrode The low density leads to low overall current injection efficiency, thereby reducing the light extraction efficiency of the light emitting diode.

Patterning the surface layer of the P-GaP AlGaInP chip and evaporating ITO transparent conductive film can reduce the total reflection of light and increase the light extraction efficiency of the chip. The methods of patterning the P-GaP layer include wet etching, nanoimprinting technology, and focused ion beam Etching creates small holes on the surface all the time, which can improve the light extraction efficiency.

Roughening the surface layer of P-GaP AlGaInP chip and evaporating ITO transparent conductive film can reduce the total reflection of light and increase the light extraction efficiency of the chip. The method of patterning the P-GaP layer mainly uses iodic acid: hydrofluoric acid: glacial acetic acid mixture, The roughening time is 90s, the roughening depth is 100-500nm, and the surface is roughened with uniform roughness, which can improve the light extraction efficiency.

The above schemes all use the good current expansion ability of the transparent indium tin oxide film, and the electrode passes through the transparent indium tin oxide film, thereby reducing the accumulation of current under the electrode, reducing the invalid injection of current, and improving the luminous efficiency. However, In in indium tin oxide (ITO) is a scarce resource, expensive and toxic. It is hoped to find a transparent material to replace ITO.

Contents of the invention

The purpose of the present invention is to provide a high-brightness AlGaInP light-emitting diode with an AZO roughened layer that has lower production cost and can improve luminous efficiency.

The invention includes a P electrode and an N electrode, the N electrode is arranged on the back of the substrate, and the N-GaAs buffer layer, the AlAs/AlGaAs reflective layer, the N-AlGaInP lower confinement layer, the MQW multi-quantum well active layer, The P-AlGaInP upper confinement layer, the P-GaInP buffer layer and the P-GaP current spreading layer are characterized in that an AZO transparent conductive layer is arranged on the surface of the P-GaP current spreading layer, and the P electrode is arranged on the surface of a part of the AZO transparent conductive layer, An AZO roughening layer is arranged on the surface of another part of the AZO transparent conductive layer.

Al-doped ZnO (ie AZO) transparent conductive film has excellent transmission characteristics, and ZnO has a wide range of sources, low price, and its stability in H plasma is better than ITO. The AZO transparent conductive layer of the present invention has good current expansion ability, and the current passes through the AZO transparent conductive layer and the AZO roughened layer, and the current is uniformly injected into the entire chip surface, thereby reducing the accumulation of current in a local area and improving the effective current. Efficiency, the AZO roughening layer uses chemical wet roughening to produce a uniform rough shape on the surface, which improves the luminous efficiency.

Furthermore, the thickness of the AZO transparent conductive layer of the present invention is 150-550 nm, which is the optimum thickness calculated by AlGaInP emission wavelength, and can be conveniently vapor-deposited by magnetron sputtering.

The thickness of the AZO roughened layer is 50-500nm. AZO roughening layer is to roughen AZO with acid or alkali wet method to reduce the occurrence of total reflection on the P-GaP surface and improve the light extraction efficiency. The current flows into the AZO transparent film layer through the P electrode. The lateral resistance of the AZO transparent film layer is smaller than the contact resistance of the P-GaP current spreading layer of the same layer. After the current expands laterally in the AZO transparent film layer, it is injected into the P-GaP current spreading layer. , and then into the active layer, which greatly improves the current injection efficiency and improves the luminous brightness of the light-emitting diode. At the same time, due to the simple process, it has the advantages of low cost and high yield of the traditional structure light-emitting diode. It is suitable for mass production and is conducive to obtaining high-quality, Low cost product.

Another object of the present invention is to propose a method for the manufacture of the above product.

The inventive method comprises the steps:

1) By MOCVD method, N-GaAs buffer layer, AlAs/AlGaAs reflective layer, N-AlGaInP lower confinement layer, MQW multi-quantum well active layer, P-AlGaInP upper confinement layer, P-GaInP buffer layer are sequentially formed on one side of the substrate layer and P-GaP current spreading layer to obtain epitaxial chips;

2) Fabricate a SiO ₂ layer on the surface of the P-GaP current spreading layer of the epitaxial chip, and under the protection of the SiO ₂ layer, etch the GaP layer in the P-GaP current spreading layer in the P electrode setting area to form a P electrode reserved hole ;

3) After removing the remaining SiO ₂ layer, evaporate the AZO transparent conductive layer on the surface of the exposed P-GaP current spreading layer;

4) Use acid or alkali solution as the roughening solution to roughen the surface of the AZO transparent conductive layer outside the reserved hole of the P electrode;

5) Fabricate and form P electrodes in the reserved holes for P electrodes, and fabricate and form N electrodes on the other side of the substrate.

The method of the invention is simple and reasonable, especially the AZO transparent conductive layer is relatively easy to roughen, and is transparent and conductive, the source material is convenient to take, and the formed product has good stability and high yield.

In order to ensure that the current spreads as much as possible laterally when passing through the AZO transparent conductive layer, and to improve the effective injection efficiency of the current, the thickness of the P-GaP current spreading layer formed during the production of the epitaxial chip in the present invention is 2 to 4.5 μm, which is suitable for P- The etching depth of the GaP layer in the GaP current spreading layer is 0.1-1 μm.

When the P-GaP current spreading layer is fabricated, magnesium is used as the doping material, and the magnesium doping concentration is 8×10 ¹⁷ cm ^-3 to 1×10 ¹⁹ cm ^-3 . The high-concentration doping of the P-GaP current expansion layer is to reduce the contact barrier with the AZO transparent conductive layer, improve the distribution of current injection, effectively improve the current injection efficiency, and increase the luminous intensity of the light-emitting diode.

After roughening the surface of the AZO transparent conductive layer outside the P electrode reserved hole, the thickness of the AZO roughened layer outside the P electrode reserved hole is 50-500nm. The thickness of the AZO transparent conductive layer between the layers is 150-550nm.

The depth of roughening the surface of the AZO transparent conductive layer is 100-500 nm. The roughening depth cannot be too deep, otherwise it will affect the light extraction efficiency.

When performing roughening treatment on the surface of the AZO transparent conductive layer, the temperature of the roughening solution used is 20-80°C. The process temperature range is relatively large, which is convenient for process operation.

In order to increase the light transmittance of the AZO transparent conductive layer, reduce the volume resistance of the AZO transparent conductive layer, enhance the adhesion with the P-GaP current spreading layer, and ensure the good electrical contact between the substrate GaAs and the N electrode, the AZO thick The high-brightness AlGaInP light-emitting diodes undergo rapid annealing treatment, the rapid annealing temperature is 380-580°C, and the annealing time is 5-20s.

Description of drawings

Fig. 1 is a kind of structure diagram of the present invention.

FIG. 2 is a top view of FIG. 1 .

detailed description

The present invention is further described in conjunction with drawings and implementation.

1. Manufacturing specific implementation steps:

1. Fabrication of epitaxial chips by MOCVD technology: N-GaAs buffer layer 200, AlAs/AlGaAs reflective layer 201, N-AlGaInP lower confinement layer 202, MQW multi-quantum well active layer 203, a P-AlGaInP upper confinement layer 204, a P-GaInP buffer layer 205, and a P-GaP current spreading layer 206, wherein the thickness of the P-GaP current spreading layer 206 highly doped with magnesium is 4.5 μm to ensure that a good For ohmic contact, the doping concentration of magnesium is 8×10 ¹⁷ cm ^-3 to 1×10 ¹⁹ cm ^-3 .

2. Clean the P-GaP current spreading layer 206 of the epitaxial chip with 215, 511 solution, deposit a layer of SiO ₂ on the surface by PECVD, spin-coat positive photoresist on the SiO ₂ layer, bake and expose , bake, and develop the chip through a high-speed spin-dryer, and after plasma gluing, the SiO ₂ layer photolithography is completed, and the SiO ₂ layer opening pattern is etched with a HF solution, and the surface is spin-coated with a degumming solution to remove the positive polarity. Photoresist, using a SiO ₂ layer opening pattern, using a mixed solution of KOH, FeCl ₃ , potassium ferrite and water (volume ratio 3:1:1:1) to etch and remove part of the GaP in the P-GaP current spreading layer 206 The etching depth of the layer is 0.1-1 μm, the etching time is 30 seconds, the temperature is 20-40 degrees, and the etching depth is 200 nm. Then use the HF solution to remove the SiO ₂ layer to complete the preparation of the electrode reserved hole 300 .

Then, the AZO transparent conductive layer 207 with a thickness of 300-500 nm is vapor-deposited on the P-GaP current spreading layer 206 by magnetron sputtering. The transmittance of the AZO transparent conductive layer 207 is guaranteed to be above 90%, and the sheet resistance is 20. Within Ώ.

3. Spin-coat positive photoresist on the AZO transparent conductive layer 207, after baking, exposure, baking, and development, the chip is spin-dried by a high-speed spin-dryer and glued with plasma, and the electrode reserved hole is engraved. , so as to protect the electrode reserved hole 300 from being roughened.

The coarsening solution can be an acid solution at 20-80°C or an alkali solution. The main components of the acid solution are: HCl, H ₂ O ₂ and water in a volume ratio of 3:1:1, or several The mixing of HCl and CH ₃ COOH can also be mixed at a volume ratio of 3:1; the main components of the alkaline solution are KOH, H ₂ O ₂ and water, or NaOH and water are mixed at a volume ratio of 2:1 , or a mixture of several.

The etching time is 5-300S, and the roughening depth is 100-500nm. The roughening depth should not be too deep, otherwise the light extraction efficiency will be affected.

The surface spin-coated positive photoresist is removed by the glue remover, that is, the AZO roughening layer 208 is completed.

After the surface of the AZO transparent conductive layer 207 outside the P electrode reserved hole 300 is roughened, the thickness of the AZO roughened layer 208 formed outside the P electrode reserved hole 300 is 50-500 nm. The thickness of the AZO transparent conductive layer 207 between the P-GaP current spreading layer 206 is 150-550 nm.

4. Use acetone and IPA solution to ultrasonically clean the chip with AZO roughening layer 208 for 10 minutes, spin-coat negative photoresist, bake, expose, bake, and develop the sample through a high-speed spin dryer. After gluing, electron beam evaporation is used to evaporate the P electrode 301. The materials of the P electrode are Cr, Ti, and Al, and the thicknesses are 50nm, 300nm, and 3500nm respectively. The negative photoresist is removed by stripping.

The size of the P electrode 301 should be smaller than the size of the electrode reserved hole 300, so as to ensure that the surface of the P electrode 301 is smooth, which is beneficial for chip bonding.

5. Attach the chip with the finished P electrode 301 on the grinding disc, and thin the back GaAs substrate 100 to a thickness of 160-200 μm.

6. Use acetone and IPA solution to ultrasonically clean the thinned chips for 10 minutes, and make N electrodes 302 on the substrate GaAs100 surface by electron beam evaporation. The N electrode materials are AuGe and Au, and the thicknesses are 120nm and 150nm respectively. .

7. Place the chip with the N-side electrode 302 in an annealing furnace for rapid annealing at an annealing temperature of 380-580°C (450°C in this example), and an annealing time of 5-20s (20s in this example).

So far, the fabrication of patterned high-brightness AlGaInP light-emitting diodes has been completed.

2. Product structure features:

As shown in Figures 1 and 2, an N-GaAs buffer layer 200, an AlAs/AlGaAs reflective layer 201, an N-AlGaInP lower confinement layer 202, an MQW multi-quantum well active layer 203, a P-AlGaInP The upper confinement layer 204, the P-GaInP buffer layer 205, the P-GaP current spreading layer 206, and the electrode reservation hole 300 is formed on the P-GaP current spreading layer 206, and the AZO transparent conductive layer 207, the P electrode 301 is arranged on the surface of part of the AZO transparent conductive layer 207, and the AZO rough layer 208 is arranged on the surface of the other part of the AZO transparent conductive layer 207. The N electrode 302 is provided on the back surface of the GaAs substrate 100 .

Since the electrode reserved hole 300 has a destructive effect on GaP, it will reduce the probability of current injection into the MQW layer through the bottom of the electrode, and improve the effective injection of current. In the present invention, the AZO transparent conductive layer 207 is formed on the surface of the P-GaP current spreading layer 206 by evaporation. The AZO transparent conductive layer 207 has good current spreading ability, and the current is injected into the entire chip surface after passing through the AZO transparent conductive layer 207, which can improve the injection efficiency of the current, and the AZO roughened layer 208 of the present invention can reduce the total reflection probability of photons, The luminous efficiency is improved, thereby improving the brightness of the AlGaInP light-emitting diode.

The P-GaP current spreading layer 206 uses SiO ₂ as a mask, and the GaP layer with a thickness of 0.1-1 μm will be etched away at the position below the electrode of the P-GaP current spreading layer 206 to form an electrode reserved hole 300 to ensure that the current passes through the AZO The transparent conductive layer 207 expands laterally as much as possible to improve the effective injection efficiency of current.

The above embodiments do not limit the present invention, and those skilled in the art can make equivalent changes or transformations without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention.

Claims (10)

1. High-brightness AlGaInP light-emitting diode with AZO roughening layer, including P electrode and N electrode, N electrode is set on the back of the substrate, and N-GaAs buffer layer, AlAs/AlGaAs reflective layer, N-AlGaInP are set on the front of the substrate in sequence The lower confinement layer, the MQW multiple quantum well active layer, the P-AlGaInP upper confinement layer, the P-GaInP buffer layer and the P-GaP current spreading layer are characterized in that an AZO transparent conductive layer is set on the surface of the P-GaP current spreading layer. The P electrode is arranged on the surface of part of the AZO transparent conductive layer, and an AZO roughened layer is arranged on the surface of the other part of the AZO transparent conductive layer. 2. The high-brightness AlGaInP light-emitting diode with an AZO roughened layer according to claim 1, characterized in that the thickness of the AZO transparent conductive layer is 150-550 nm. 3. The high-brightness AlGaInP light-emitting diode with an AZO roughened layer according to claim 1 or 2, characterized in that the thickness of the AZO roughened layer is 50-500 nm. 4. The method for manufacturing a high-brightness AlGaInP light-emitting diode with an AZO roughening layer as claimed in claim 1, comprising sequentially forming an N-GaAs buffer layer, an AlAs/AlGaAs reflective layer, and an N-AlGaInP lower layer on one side of the substrate by the MOCVD method. Confinement layer, MQW multi-quantum well active layer, P-AlGaInP upper confinement layer, P-GaInP buffer layer and P-GaP current spreading layer to obtain epitaxial chips; P electrodes and N electrodes are formed on the epitaxial chips respectively; It is characterized in that: a SiO ₂ layer is fabricated on the surface of the P-GaP current spreading layer of the epitaxial chip, and under the protection of the SiO ₂ layer, the P-GaP current spreading layer in the area where the P electrode is set is etched to form a reserved hole for the P electrode; After removing the remaining _SiO2 layer, vapor-deposit the AZO transparent conductive layer on the surface of the exposed P-GaP current spreading layer; use acid or alkali solution as the roughening solution, and the surface of the AZO transparent conductive layer outside the reserved hole for the P electrode Roughening treatment is carried out; the P electrode is arranged in the reserved hole of the P electrode. 5. The method for manufacturing a high-brightness AlGaInP light-emitting diode with an AZO roughening layer according to claim 4, characterized in that: the thickness of the P-GaP current spreading layer formed when the epitaxial chip is made is 2-4.5 μm. -GaP The etching depth of the GaP layer in the current spreading layer is 0.1-1 μm. 6. according to the manufacture method of the described high brightness AlGaInP light-emitting diode with AZO roughening layer of claim 4 or 5, it is characterized in that: when making P-GaP current spreading layer, take magnesium as dopant material, magnesium doping concentration 8×10 ¹⁷ cm ^-3 to 1×10 ¹⁹ cm ^-3 . 7. The method for manufacturing a high-brightness AlGaInP light-emitting diode with an AZO roughening layer according to claim 4, characterized in that: after the surface of the AZO transparent conductive layer on the outside of the P electrode reserved hole is roughened, the P electrode The thickness of the AZO roughening layer outside the reserved hole is 50-500nm, and the thickness of the AZO transparent conductive layer between the AZO roughening layer and the P-GaP current spreading layer is 150-550nm. 8 . The method for manufacturing a high-brightness AlGaInP light-emitting diode with an AZO roughened layer according to claim 4 , wherein the depth of roughening the surface of the AZO transparent conductive layer is 100-500 nm. The roughening depth cannot be too deep, otherwise it will affect the light extraction efficiency. 9 . The method for manufacturing a high-brightness AlGaInP light-emitting diode with an AZO roughening layer according to claim 4 , wherein the temperature of the roughening solution is 20-80° C. 10. The manufacturing method of the high-brightness AlGaInP light-emitting diode with AZO roughened layer according to claim 4, characterized in that: after the P electrode and N electrode are formed, the semi-finished product is annealed at an ambient temperature of 380-580°C 5~20s.